I'm trying to see the shape of the leaves to know what kind of locust, I think it is honey-locust? Do you know the cultivar name, e.g. 'Skyline', 'Shademaster' etc? I have 'Shademaster' and it tends to grow long branches parallel to the ground but the problem in your case seems to be that it's all at the top? It may help if we could see the whole tree from ground up and maybe from another angle. It would be easier to see what to do also after the leaves fall.